A fluid energy machine, such as a gas turbine, a steam turbine, a compressor or the like, comprises at least one rotor assembly and at least one stator assembly. For optimal operation of a rotor assembly it is necessary that rotor components of the rotor assembly are arranged concentrically with respect to a rotation axis of the rotor assembly.
Therefore, during initial building of a rotor assembly, the concentricity of the rotor components with respect to the rotation axis of the rotor assembly has to be checked.
For this purpose it is known to provide disc-shaped rotor components made from carbon steel having a circular surface on their radially outer contour. When checking concentricity of such a rotor disc with respect to a rotation axis of a rotor assembly the circular surface of the rotor disc can be brought into contact with a suitable measuring device, such as a dial indicator.
In use, components of the rotor assembly are exposed to working fluids. Through this, rotor components can suffer from a gradual destruction from a chemical reaction with its environment. If a circular surface of a rotor disc suffers from e. g. corrosion the circular surface gets rough in such a way that it cannot be used again, for example when a rotor assembly is serviced, for checking centricity of the rotor disc with respect to a rotation axis of a rotor assembly. Therefore, such a rotor disc becomes unserviceable and cannot be reused.
For checking concentricity of a rotor disc with respect to a rotation axis of a rotor assembly, a circular surface of a rotor disc made from carbon steel cannot viably be coated with a corrosion protection coating because an unavoidable variation of the coating thickness affects the concentricity measurement.
It is known to use rotor discs made from corrosion resistant material which can be reused after a period of service as the geometry of a circular surface of such a rotor disc is unchanged. But the corrosion resistant material is more expensive than carbon steel material.
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